In the sheet metal forming industry, stamping presses having forming dies are typically used to quickly and precisely shape a sheet metal workpart to the desired form. Automotive body parts such as deck lids, doors and quarter panels are usually formed in a stamping process. In many instances, it is not always prudent to shape the final workpart form in one stamping operation. Because of the physical properties of sheet metal and forming die construction practices, it is favored in many instances to form a workpart stamping in two or more successive forming operations. For large stampings, such as those automotive body pieces described above, separate and remotely spaced stamping presses must be employed in this successive forming operation.
In the early days of industry, such successively formed workpart stampings were manually transferred from the forming die of one stamping press to a remotely spaced successive forming die in another stamping press. Concerns for increased productivity and worker safety gradually introduced an automated shuttling process whereby the two stamping presses were synchronized to cycle in unison, with a mechanized workpart transfer assembly automatically plucking the workpart stamping from the forming die of a first stamping press and transferring that stamping to the remotely spaced forming die in a second or successive stamping press.
Examples of these prior art workpart transfer assemblies may be found in U.S. Pat. No. 4,509,638 to Kato et al, issued Apr. 9, 1985 and U.S. Pat. No. 4,523,889 to Orii, issued Jun. 18, 1985. These workpart transfer assemblies both include a stationary base positioned in a clearance space between the two stamping presses, and having some form of gripping members which reach into the respective stamping presses and alternately pluck a partially formed workpart stamping from one press and transfer it to the next successive forming die in the other stamping press. The primary deficiency of these workpart transfer assemblies reside in the relatively slow rate at which they operate. Slow operating rates require slowing of the stamping press cycle times, which in turn results in fewer workparts produced per hour.
Therefore, the workpart transfer assembly art is in need of a device which can rapidly shuttle workparts between two stamping presses with optimum reliability and of a simple construction to facilitate maintenance.